1. Field of the Invention
The invention relates to a blind arrangement with a blind web which can be unwound from a winding roller in order to at least partially cover an opening relative to the interior of a vehicle, especially a motor vehicle, and which can be wound back onto the winding roller in order to at least partially expose the opening, the blind web being provided in the transverse direction with arches and has a tension arch on its front end, the arches being guided laterally in guideways and provide convexity to the blind web in the transverse direction. Furthermore, this invention relates to a vehicle roof with such a blind arrangement.
2. Description of Related Art
Blind arrangements of the initially mentioned type are used, for example, in motor vehicles having a roof opening in a fixed roof surface which is closed and opened by means of a transparent cover. The blind arrangement is located underneath the roof opening in order to be able to regulate the light incidence through the roof opening. The use of these blind arrangements is, however, not limited to vehicle roofs. Rather, these blind arrangements can be used in the same way in windows or other compartments to be separated from the passenger compartment, for example, to separate a sleeping compartment or a high roof. To simplify the description of the blind arrangement to which the invention relates, reference will be made solely to the application thereof to vehicle roofs below.
In earlier blind arrangements, flat blind webs were used in which the blind web was tensioned by means of a stiff tension arch attached to its front edge above the roof opening. In order, on the one hand, to stiffen the blind web and so to reduce its sagging, and on the other hand, in a vehicle roof that is arched in the lengthwise direction of the vehicle, in order to not limit the head space underneath the blind arrangement by a blind web tensioned between the winding roller and the tension arch, the blind web is advantageously provided with arches which are guided laterally in guideways. Since vehicle roofs, however, are generally arched not only in the lengthwise direction of the vehicle, but also in its transverse direction, for optimum use of the space available in the passenger compartment, it is desirable to have a blind arrangement in which provisions are made for convexity of the blind web in the transverse direction of the vehicle.
International Patent Application Publication WO-A-96/01191 describes a blind arrangement of the initially mentioned type in which the distance of the guideways in which the arches are guided is selected such that, near the winding roller, it corresponds to the length of the arch, but then shortens in a transition area as the distance from the winding roller increases, so that the arches are curved transversely to the blind web upon passage through the transition area. The main defect of this approach is that inherently high frictional forces occur between the arches and the guideways. Another defect lies in the tolerance sensitivity of this structure which follows from the fact that, especially when using the blind arrangement in vehicle roofs, only a relatively slight convexity is to be produced in the transverse direction of the vehicle. However, the greater the radius of convexity to be spanned, the greater the ratio of the height of convexity to the constriction of the guideways and the narrower the tolerances to be maintained for a special desired transverse blind arch both in production and also installation of the profile components which have narrowing guideways.
Published Japanese Patent Application 63-258213 describes another attempt at an approach to the aforementioned problem. Here, the blind web is provided with arches in the transverse direction which are made of an elastic material and which, in the released state, have a convexity according to the desired transverse blind convexity. To be able to wind the blind web onto a winding roller to save space, there is a hold-down sheet in order to bend the arches when winding onto the winding roller. As a result of the high friction losses which inherently occur when bending the arches straight, in this construction approach for winding of the blind web onto the winding roller, a separate return motor is necessary; for several reasons, for example, the amount of space required, installation complexity, costs, etc. this is a disadvantage.